Railway signaling system



Aug.23,1938. TNLJUDGE RAILWAY SIGNALING SYSTEM 2 Sheets Sheet 1 FiledSept. 25, 1956 INVENTOR ATTORNEY Aug. 23, 1938. T. J. JUD GE RAILWAY SIGNALING SYSTEM Filed Sept. 25, 1956 2 Sheets-Sheet 2 INVENTOR WATTORINEY Patented Aug. 23, 1938 UNETED STATES gPATEN'i' OFHQE RAILWAYSIGNALING SYSTEM ter, N. Y.

Application September 25, 1936, Serial No. 102,557

12 Claims.

This invention relates in general to railway signaling systems, and moreparticularly to an absolute permissive block signaling system employingcoded track circuits for controlling wayside and/ or cab signals.

In general, it is proposed in accordance with the present invention toprovide an absolute permissive block signaling system employing codedtrack circuits arranged to effect the control of train movements in bothdirections through a portion of single track in the usual manner, butwithout the use of control line circuits. More specifically, it isproposed to provide in each block a track circuit associated with eachdirection of movement so arranged that the two track circuits areindependent of each other due to the distinctive character of theirenergization. It is then proposed to independently code or modulate thedistinctive energization of each of these track circuits in a manner tocondition wayside and/or cab signals for each direction of trainmovement in accordance with forward trafiic conditions.

Other objects, purposes and characteristic features of the presentinvention will be obvious as the description thereof progresses, duringwhich references will be made to the accompanying drawings, in which-Fig. 1 and Fig. 2 show in a diagrammatic and conventional manner theapparatus and circuits 3 of a portion of an absolute permissive blocksignaling system arranged in accordance with the present invention.These two figures show adjacent portions of the railway track and areintended to be placed end to end with Fig. 2 at the right.

In the accompanying drawings, a single track portion of a railway hasbeen shown as divided by insulating joints J into track sections orblocks l, 2 and 3, and it is to be understood that this is a portion ofsingle track wherein trains normally move in either direction andpassing sidings or portions of double track will be provided at spacedintervals which have not been shown.

The present system employs the usual absolute permissive block featurewherein two or more trains are permitted to follow each other throughthe portions of single track between these passing sidings, but a trainis prevented from entering any such single track portion which isoccupied by a train moving in the opposite direction. It is believedthat a description of the portion of the present signaling systemassociated with the typical intermediate portion of single trackcomprising blocks I, 2 and 3 will be sufllcient for an understanding ofthe present invention, and inasmuch as the apparatus associated witheach of these blocks is identical, the same reference characters havebeen assigned to the like pieces of apparatus with an exponentcorresponding to the particular block with which it is associated.

It may be briefly stated that in the present 5 system each block isprovided with two superimposed alternating current track circuits, thesetwo circuits being energized with distinctively different frequenciesand reversely arranged with respect to the ends of the track rails towhich the energy is applied, the track rails of course forming commonelectrical conductors for both circuits. More specifically, alternatingcurrent energy of one frequency is connected to one end of the rails ofeach block and alternating current 15 energy of a distinctivelydifferent frequency is connected to the other end of these same trackrails of each block, or as shown on the drawings, the left hand end ofthe rails of each block is connected through a transformer LTR to apower 20 line LP energized by an alternating current generator LG, whilethe right hand end of these rails of each block is connected throughsimilar transformers RTR to another power line RP energized by analternating current generator RG which supplies a different frequency ofalternating current than generator LT. It is to be understood howeverthat in the event it is not desirable to extend the power line wires LPand RP along the trackway, the two distinctive frequencies of alter- 30nating current can be generated locally at each block from a battery orthe like such as by vibrating reed contacts operating at distinctivelydifferent frequencies and arranged to interrupt the energization of theprimary of transformers LTR and RTR respectively, all in accordance withwell recognized principles.

The particular frequency applied to each end of each block is conductedthrough the track rails in series to operate a track relay at the otherend, which track relay is rendered nonresponsive to the differentfrequency applied at the same end. More specifically, the energy appliedto the left hand end of each section through transformers LTR isconducted through the rails in series to the primary of a tuningtransformer RTA connected across the right hand end of the rails, thesecondary of this transformer RTA being connected to the primary of asecond tuning transformer R'I'B through a tuning condenser RC, wherebythe secondary of the transformer RTB is only effectively energized bythe alternating current of the frequency supplied by transformer LTR andis not eifectively energized by the alternating current of the frequencysupplied by transformer RTR. Similar transformers LTA and LTB andcondenser LC are employed at the left hand end of each section, but thecondenser LC as indicated is of a capacity different from condenser RCso that the secondary of transformer LTB is only effectively energizedby the alternating current of the frequency supplied by transformer RTR.

The secondary of transformer RTB energizes a direct current track relayRT through a full-wave rectifier RR and in a similar manner thesecondary of transformer LTB energizes a second direct current trackrelay LT through a full-wave rectifier LR. In this manner, the trackrelay RT is controlled only by the current from the transformer LTR andtrack relay LT and is controlled only by the current from thetransformer RTR, and inasmuch as the current from both transformers LTRand RTR flows through the track rails in series, both of these trackrelays LT and RT will be dropped by a train shunting the associatedtrack section.

In order to communicate the traffic conditions from block to blockwithout the use of control line circuits, the alternating currentenergization of each of the two track circuits for each of the blocks isindividually modulated or coded in accordance with traffic conditions ina direction individually associated with each of thesetwo circuits. Inother words, the secondary of transformer LTR is connected to the trackrails through a back contact of a code repeater relay LCP which isoperated in synchronism with either contact C or CWO of a modulator orcoder C, and. in a similar manner, the secondary of transformer RTR isconnected to the track rails through a back contact of a code repeaterrelay RCP likewise operated in synchronism with either of contacts CV5or C188 of a similar coder C.

The contacts C75 and CESB may be operated in any suitable manner, butfor convenience these contacts have been diagrammatically illustrated asoperated'by the usual form of mechanical coding means wherein acontinuously energized motor M mechanically operates contacts C75 at therate of '7 5 times per minute and also operates contact C 86 at the rateoftimes per minute. The code repeating relays LCP and RCP are at timescontinuously deenergized, and at other times operated by either contactC15 or contact CIBI] as selected by traffic conditions as will be laterdescribed.

It will now be clear that when the code repeating relays LCP and RCP areoperating to interrupt their associated track circuits at either the '75or the 180 code rate, the respective track relays LT and RT are operatedin synchronism therewith, and consequently the rate of operation of thearmatures of relays LT and RT as affecting certain decoding meansdetermined the respective forward trafiic conditions. The decoding meanscontrolled by both track relays LT and RT is identical and comprisesrespective transformers LTD and RTD having a center tapped primaryconnected to one side of a direct current source of energy while the twoextreme ends are alternately connected to the other side of this sourceof energy by front and back contacts of the respective track relay LT orRT. In this manner, alternating current isinduced in the secondaries oftransformers LTD and RTD which is proportional in frequency to the rateof operation of the respective track relays LT and RT.

Decoding transformers LTE' and RTE are provided having primary windingsconnected across the secondary of transformers LTD and RTD respectivelythrough condensers LCE and RCE respectively, which condensers are of avalue selected to resonate or to permit an effective alterhating currentvoltage in the secondary of transformers LTE and RTE only when thefrequency of alternating current from the secondary of transformers LTDand RTD is provided by the 180 rate of operation of the track relays LTand RT respectively. Similar tuning transformers LT? and RTF are alsoconnected across the secondary of transformers LTD and RTD respectivelybut through different capacity condensers LCF and RCF whereby aneffective alternating current voltage is permitted in the secondary oftransformers LTF and RTF only when the frequency of alternating currentfrom the secondary of transformers LTD and RTD is produced by either the180 code rate or the 75 code rate of operation of the respective trackrelays LT and RT. The alternating current produced in the secondary oftransformers LTE and RTE energize respective direct current relays LE8!)and RES!) through respective full-wave rectifiers LRE and RRE, andlikewise the alternating current produced in the secondaries oftransformers LTF and RTE energize respective direct current relays Ll?and Rl'5 through respective full-wave rectifiers LRF and RRF.

.The track relays LT and RT also control the energization of respectiveslow releasing track repeating relays LT? and RT? whereby theserepeating relays remain picked up either when the associated track relayis continuously energized or is operating at the 75 or 180 code rate,but drop when the associated track relay is continuously deenergized. Itwill now be clear that when the track relays are continuously energized,the associated repeating relays will be picked up but both theassociated 180 and 75 decoding relays will be dropped; and when thetrack relays are operated at the 180 code rate, the respective repeatingrelays and both the respective 180 and 75 decoding relays will be pickedup; but when operating at the '75 code rate, the respective '75 decodingrelays and the respective repeating relays only will pick up; andobviously when the track relays are continuously deenergized due to atrain shunt for example, all of these'relays will be dropped.

A direction stick relay LS and RS is also associated with each block,which stick relays are made slow releasing for a purpose laterdescribed. These directional stick relays LS and RS are selectivelyenergized according to the direction of a train movement over theassociated portion of track, or that is, relay LS is picked up by aneast bound train movement and relay RS is picked up by a west boundtrain movement.

The present wayside equipment may be employed to control either waysideor cab signals or both, and consequently the method of effecting thecontrol of both types of signals has been shown in the accompanyingdrawings, although it is to be understood that train movements areadequately protected by either type and consequently either wayside oncab signals may be employed alone and the other omitted from the system.

The wayside signals have been illustrated as the three indicationmultiple unit color light type although other types may be equally wellemployed, and the change in the controlling circuits necessary whenusing these other types will be obvious to those skilled in the railwaysignaling art. The

wayside signals ES govern traflic in east bound direction through theirassociated block and are jointly controlled by the associated decodingrelays LI8I! and L15, and likewise the wayside signals WS govern traficin a west bound direction and are jointly controlled by the decodingrelays RIBIJ and R15.

A west bound train represented by wheels and axle 5 has been shown asoccupying section 3 of Fig. 2, and a cab signal system which may beemployed in the present system has been shown diagrammatically ascarried by such train, but it is to be understood that the particulararrangement of such car carried equipment is shown merely for an exampleand that various other well known types of car carried signalcontrolling systems can equally well be employed.

In Fig. 2, the car carried equipment is illustrated as comprisingreceiver coils 6 and 1 carried on the train above the rails and in frontof the first pair of wheels and axle whereby current is induced in thesereceiver coils by the alternating current flowing in the track railsfrom transformer LTR A means similar to that employed in the waysideequipment may be used to tune the circuit of the receiver coils to theparticular frequency of alternating current received from the rails, orthat is, the receiver coils 6 and 1 are connected in series to theprimary of a tuning transformer 8, the secondary of transformer 8 beingconnected to the primary of a second transformer 9 through a condenserI0 whereby the secondary of transformer 9 is only effectively energizedby the alternating current of the frequency provided by transformers LTRwhen the train is traveling in a west bound direction.

However, when the same train is traveling in an east bound direction,the alternating current affecting the receiver coils will be of adifferent frequency supplied by transformers RTR, and consequently it iscontemplated that a manually operable switch II may be provided which inthis case of an east bound direction of movement will be moved from itswest bound position W to its east bound position E to connect acondenser I2 in multiple with condenser I I], and thus tune this circuitto the frequency of transformer RTR. However, it may be consideredsufficient in some applications to arrange the tuning of the car carriedreceiver circuit sufiiciently broad so that the secondary of transformer9 will be effectively energized by the frequency of current receivedfrom either transformers LTR or RTR, and in such case the switch I I andcondenser I2 may be omitted.

The remaining portion of the car carried equipment may be constructed inaccordance with the usual practice and has been illustrateddiagrammatically as an amplifying means A amplifying the current fromthe secondary of transformer 9 to a value which can operate a masterrelay MR. The master relay MR, then operates in synchronism with theoperation of the particular code repeating relays LCP or RCR the same asthe track relays LT and RT, and consequently a decoding means similar tothat employed in the wayside arrangement may be employed.

This car carried decoding means comprises a transformer I4 operating thesame as transformer RTE in the wayside equipment but from a contact ofthe master relay MR rather than a track relay RT. The output oftransformer I 4 then energizes a decoding relay D I 80 through rectifierI5, tuning transformer I6 and condenser I6 only when the 180 code rateis received from the rails,

and the output of transformer I4 likewise energizes a decoding relay D15through rectifier I9, transformer 20 and condenser 2| when the or the180 code rate is received, all in a manner which may be understood fromthe previous description of the wayside decoding equipment.

Having now pointed out the essential elements of the present system, itis believed that the usefulness and the various interrelated functionsof the apparatus and circuits of the present embodiment will be morereadily understood by vfurther description being given from thestandpoint of operation.

Operation Considering that the illustrated west bound train representedby wheels and axle'5 is the only train traversing the portion of therailway system under consideration, this train then receives a clear orgreen cab signal as well as a green wayside signal. In other words,sections I and 2 being unoccupied, the code repeating relay LCP is con"nected to contacts CI of coder C through front contact 25 of relay RTPand front contact 26 of relay R15 thereby operating contact 21 of relayLCP to impulse the energization of section 2 from transformer LTR. atthe rate of 180 times per minute which picks up the track repeater relayRTP at front contact 32 of relay RT and the decoding relays R15 andRIBIl are also energized by the operation of contact 33 of relay RT Thegreen signal lamp G of signal WS is then ener' gized through frontcontact 28 of relay R15 and front contact 29 of relay RI8U In a likemanner the green light G at signal WS is energized through frontcontacts 48 and 49 of relays R15 and RI 35 respectively, and at all westbound signals as far as the next passing track at the left of theillustrated portion of single track, a green signal will likewise bedisplayed.

The present train while occupying section 3 also receives a green cabsignal due to the fact that code repeater relay LCP is connected tocontact CISQ of coder C2 through front contact Si! of relay RTF andfront contact ill of relay R15 thereby operating contact 60 to impulsethe energization of section 3 from transformer LTR at the 180 code rate.The reception of these 180 code impulses by receivers 6 and 'I thenoperates contact I3 of the master relay ME to effect the energization ofrelays D15 and DI Bil as previously described, and the green cab signalG is then energized through front contacts 34 and 35 of relays D15 andDISI] respectively. The east bound signal ES however, properly displaysa red or danger indication due to the continuous deenergization of trackrelay LT caused by the occupancy of section 3, thus dropping relay LTPat open front contact 38, and dropping relays LI8IJ and L15 due to theinaction of contact 31, and the red signal lamp R of signal ES is thenenergized through back contact 38 of relay L15 The LTP and L15 relaysand the east bound stick relay LS being deenergized, obviously preventsenergization of the code repeater relay RCP thus continuously supplyingthe right hand end of section 2 with alternating current fromtransformer RTR through back contact 39 whereby track relay LT iscontinuously energized to drop the decoding relays LIBil and L15 by theinaction of contact ill, and the red lamp R of the east bound signal E6is then energized through back contact M of relay L15 Likewise thedeenergization' of the decoding relay L and the east bound stick relayLS prevents the energization of the code repeating relay RCPthussupplying continuous energy to the right hand end of section i fromtransformer RTE through its back contact ill, and it will be clearthatthe right hand end of each section in advance of the Considering nowthat the present train in Fig.

2 passes the insulating joints J and enters section 2, it will be clearthat track relay RT will now be continuously deenergized to drop thedecoding relays Rl'5 and BMW and energizes the red signal lamp R atsignal WS through back contact 23 of relay BT5 The car-carried receiversS and 7 however, DOW receive current llTlpulses of the 180 coderate fromtransformer LTR which obviously maintains the green cab signal Genergized the same as while occupying block 3.

When the present train is passing the insulating joints J separatingblocks 2 and 3, it will be clear that the track repeating relays RTP andLTP will both be deenergized by contacts 32 and 35 respectively, andalthough these track repeater relays are necessarily somewhat slowreleasing the decoding relays are necessarily still slower to releasedue to the shunt across their windings provided by the associatedfull-wave rectifiers. Consequently the track repeater relay RTP willdrop before the decoding relay EH3 drops, and a circuit is thenmomentarily completed to pick up the west bound stick relay RS whichcircuit may be track from back contact 42 of relay RTP back contact 43of relay LTP front contact M of relay RS55 through the windings of relayRS to hen the stick relay RS has picked up, it will be clear that relayR15 subsequently drops, and a stick circuit is then completed throughfront contact 45 of relay RS and back contact 4 3 of relay R775 to holdrelay RS in its picked up condition, the stick relay RS beingsufficiently slow releasing to retain its armature in its attractedposition during the momentary interruption of .its energization causedby the movement of contact 44.

The entrance of the present train into block it obviously disconnectsthe code repeating relay LCP from the contact ClSii of the coder C atfront contacts 30 and 3d of relays RTP and R75 respectively, but whenthe west bound stick relay Rs picks up, the code repeating relay LCP isconnected to contact C15 of the coder C through front contact 66 of therelay RS In this manner the entrance of the present train into section'2 changes the energization of section from transformer L'TR, from the180 code rate to the '75 code rate.

Now considering that the present train traverses section 2 and enterssection I of Fig. 1, it will be clear that track relay RT will drop andthe decoding relays R35 and R586 will be deenergized due to the inactionof contact iii, thus changing the indication at signal WS from a greento a danger or red indication by energizing the red lamp B through backcontact 48 of relay R15 Likewise when the present train passes theinsulating joints J separating sections l and 2, the dropping of thetrack repeater relay RJP before the dropping of the decoding relay R15establishes a pick up circuit for the west bound stick relay RS whichcircuit may be traced from back contact 50 of relay RTP back contact 5!of relay LTP front contact 52 of relay R15 through the windings of relayRS to A similar stick circuit is completed upon the subsequent droppingof relay R15 to hold up relay RS through its stick contact 53, and thedropping of relays RTP and R15 disconnected the code repeating relay LCPfrom the Cl code contact at open front contacts 25 and 26 respectively,and the picking up of the stick relay RS connects the LCP relay to thecontact C15 of the coder C through its front contact 55.

The coder repeating relay LCP now interrupts the energization of section2 from transformer LTR. at the 75 code rate by its contact 2?, which inan obvious manner picks up relay R75 in Fig. 2 but allows relay RIBEI toremain deenergized. A caution signal indication is then displayed atsignal WS by energizing the yellow signal lamp Y through front contact28 of relay R 55 and back contact 29 of relay REBU The picking up of thedecoding relay R15 ob viously releases the west bound stick relay RS atcontact M inasmuch as the repeating relays RTP and LTP are now bothpicked up, and the code repeating relay LCP is disconnected from codercontact C75 at open front contact 46 of relay RS and is again connectedto coder con tact C980 through front contacts 30 and M of o relays RTPand R75 respectively. The energization of section 3 from transformerLTRF' is now interrupted at the code rate by contact 6! of relay LCPwhich in an obvious manner provides a clear west bound signal at theentrance to section 3, which signal hasrnot been shown in theaccompanying drawings.

In this manner, it will be seen that a train traversing a portion ofsingle track picks up the stick relays associated with its particulardirec tion of travel to allow a second train traveling in the samedirection to follow at a safe distance in the rear of this first train.However, it may be seen that the stick relays associated with theopposite direction of travel do not pick up, or that is, considering thepresent west bound train movement, it is evident that the entrance ofthe present train into section 3 before section 2 causes the relay L75to be deenergized before the pick up circuit for stick relay LS isclosed at back contacts 32 and 3 3 of relays RTP and LTP respectively.

It will of course be clear that the three different cab signalindications are displayed on the train in the same manner as at thewayside signals, or that is, a green cab signal G is energized aspreviously described by the reception of the 180 code rate of impulsesby the receivers 6 and i, while the reception of the '75 code rate ofimpulses drops relay Ditii and completes an energizing circuit for theyellow cab signal Y through front contact 34 and back contact 35 ofrelays D15 and Dita respectively, and the reception of eitheruninterrupted alternating cur rent or the reception of no current by thereceivers B and l obviously deenergizes both relays D'l5 and D589] toenergize the red signal lamp R through'back contacts 34 and 55 of relaysD'l5 and D! 89 respectively.

The operation of the apparatus of the present system associated with aneast bound train movement is similar in every respect to the operationjust described of the apparatus associated with a west bound movement,and consequently it is believed unnecessary to describe such operationin detail. The stick relays LS are of course picked up by an east boundtrain movement to allow east bound trains to follow in the same mannerthat relays RS were picked up by a west bound movement, and the westbound wayside signals WS then all display a stop indication in a similarmanner during such an east bound movement. Likewise during an east boundmovement of the illustrated train, the switch ii is moved to position Eas previously described whereby to tune the receiver circuit to thefrequency of alternating current supplied by transformer RTR, andotherwise the car carried equipment functions the same as during a westbound movement.

An absolute permissive block signaling system has thus been providedwherein three-indication wayside and/or cab signals are controlledwithout the use of control line circuits to permit following trainmovements through portions of single track but to prevent a train fromentering a portion of single track which is occupied by a train movingin the opposite direction. The feature of the present inventionpermitting such double direction operation without control line circuitsin, the arrangement of superimposed alternating current track circuits.These track circuits, although each having the track rails as commonconductors are in effect two separate and distinct circuits, eachcircuit being individually coded and associated with one particulardirection of travel. These circuits are also reversely arranged withrespect to the ends of the track rails towhich energy is applied so thateach direction of train movement progresses toward the source of energyin the circuit associated with that direction of movement, therebypermitting cab signal equipment to be properly controlled during eachdirection of movement and enabling traflic conditions at each block tobe transmitted to the rear blocks in each direction by the respectivecircuit.

Another important feature of the present system is the method ofeffecting a stop indication at all signals governing traffic in adirection opposite toan established train movement. This method consistsin supplying uninterrupted alternating current to the track circuit ofeach block associated with such opposite direction of traffic, whichuninterrupted alternating current effects a stop indication at allsignals controlled thereby. A particular advantage of this feature isthat the track circuits are still able to detect between the occupiedand the unoccupied condition of their associated blocks, andconsequently other apparatus such as highway crossing signals may beconditioned directly by the track relays or the track repeater relays ofthese blocks in the usual manner.

The above rather specific description of one form of the presentinvention has been given solely by way of example, and is not intendedin any manner whatsoever in a limiting sense. It is to be understoodthat various modifications, adaptations and alterations may be appliedto meet the requirements of practice, without in any manner departingfrom the spirit or scope of the invention, except as limited by theappended claims.

What I claim is:

1. In a single track railway signaling system, a plurality of insulatedtrack sections, means for applying alternating current of a firstfrequency to one end of each section, means for applying alternatingcurrent of a second frequency to the other end of each section, a trackrelay at said one end of each section responsive only to the alternatingcurrent of the second frequency, a track relay at said other end of eachsection responsive only to the alternating current of the firstfrequency, means for distinctively coding the alternating current of thefirst frequency in accordance with traflic conditions in one direction,means for distinctively coding the alternating current of the secondfrequency in accordance with trafiic conditions in the other direction,and decoding means individually controlled by each track relay anddistinctively responsive to the coding of the associated frequency ofalternating current.

2. In a single track railway signaling system, a plurality of insulatedtrack sections, means for applying alternating current of a firstfrequency to a first end of each section, means for applying alternatingcurrent of a second frequency to the second end of each section, a trackrelay at said first end of each section responsive only to thealternating current of said second frequency, a track relay at saidsecond end of each section responsive only to the alternating current ofsaid first frequency, means for distinctively coding the alternatingcurrent of said first frequency in accordance with trafiic conditions inone direction, means for distinctively coding the alternating current ofsaid second frequency in accordance with traffic conditions in the otherdi rection, decoding means individually controlled by each track relayand distinctively responsive to the coding of the associated frequencyof alternating current, and wayside signals controlled by the decodingmeans.

3. In a railway signaling system, a portion of single track divided intoinsulated track sections, means for simultaneously applying differentlycharacterized energy to opposite ends of each section, a track relay ateach end of each section responsive only to the energy applied to theopposite end, means for individually impulsing the energy applied toeach end of each section to form codes according to trafiic conditions,and decoding means operated by each track relay for distinctivelyresponding to said codes.

4. In a railway signaling system, a portion of single track divided intoinsulated track sections, means for simultaneously applying differentlycharacterized energy to opposite ends of each section, a track relay ateach end of each section responsive only to the energy applied to theopposite end, means for impulsing the energy applied to one end or tothe other end of each section in accordance with the direction ofmovement of a train through the portion of single track, and signalcontrolling means at each section distinctively conditioned by theimpulsing of the energy applied to the associated section.

5. In a railway signaling system, a portion of single track divided intoinsulated track sections, means for applying interrupted alternatingcurrent of one frequency to the exit end of each section for eachdirection of train movement thereover, means for simultaneouslytherewith applying uninterrupted alternating current of a differentfrequency to the entrance end of each section for each direction oftrain movement thereover, and signaling means controlled by saidinterrupted alternating current to display a clear indication andcontrolled by said uninterrupted alternating current to display a stopindication.

6. In a railway signaling system, a portion of single track divided intoa plurality of track sections, means for simultaneously applyingalternating current energy of distinctively different frequencies toopposite ends of each section, means for coding the energy applied ateach end of each section in accordance with traffic conditions in thetwo sections respectively adjacent thereto, and signal controlling meansgoverned by the coding of the energization of each section.

'7. In a railway signaling system, a portion of single track dividedinto track sections, means for simultaneously applying alternatingcurrent energy of different frequencies to opposite ends of eachsection, means for coding the energy applied to each end of each sectionin accordance with traflic conditions throughout the sectionsrespectively adjacent to each end, wayside signals responsive to thecoded energy, continuous inductive cab signaling means, and selectivemeans for rendering the cab signaling means responsive to one frequencyor to the other frequency of the alternating current energy applied tothe sections in accordance with the direction of travel.

8. In combination, a stretch of railway track divided into sections, afirst source of alternating current, a second source of alternatingcurrent of a different frequency than the first source, a code followingtrack relay at one end of each section responsive to the first source ofalternating current only, a code following track relay at the other endof each section responsive to the second source of alternating currentonly, means for supplying impulses of alternating current to eachsection from one of said sources of alternating current in accordancewith the direction of a train movement through the stretch of track,means for supplying continuous alternating current tov each section fromthe other source of alternating current, signals at each end of eachsection governing traffic in opposite directions, and signal controllingmeans controlled by each track relay for effecting a most restrictiveindication when the associated track relay is energized by continuousalternating current and for effecting lesser restrictive indicationswhen energized by impulses of alternating current.

9. In combination, a stretch of railway track divided into tracksections, each bound and west bound signals at the ends of each section,an east source of alternating current energy of one frequency at theeast end of each section, a west source of alternating current energy ofa different frequency at the west end of each section, a track relay atthe east end of each section I responsive only to the frequency ofalternating current at the west end of the section, a track relay at thewest end of each section responsive only to the frequency of alternatingcurrent at the east end of the section, means operable to intermittentlyconnect the east source of alternating current to the east end of eachsection to form codes distinctive of west bound traffic conditions,means operable to intermittently connect the west source of alternatingcurrent to the west end of each section to form codes distinctive ofeast bound trafi'ic conditions, code responsive means controlled by thetrack relay at the east end of each section for governing the west boundsignals, and code responsive means controlled by the track relay at thewest end of each section for governing the east bound signals.

10. In combination, a stretch of railway track divided into tracksections, an east source of a1- ternating current energy of onefrequency applied at the east end of each section and simultaneously awest source of alternating current energy of a different frequency atthe west end of each section, means operable to intermittently connectthe east source of alternating current to the east end of each sectionto form codes distinctive of east bound traffic conditionscontemporaneously therewith and means operable to intermittently connectthe west source of alternating current to the west end of each sectionto form codes distinctive of west bound traffic conditions.

11. In combination, a stretch of railway track divided into tracksections, means for applying alternating current of differentfrequencies to opposite ends of each section, a track relay at each endof each section responsive only to the alternating current of thefrequency applied to the opposite end, means controlled by the trackrelay at one end of each section for governing trafiic in one direction,and means controlled by the track relay at the other end of each sectionfor governing traffic in the other direction.

12. In a railway signaling system, a portion of single track dividedinto a plurality of track sections, means for simultaneously applyingalternating current energy of distinctively different frequencies toopposite ends of each section, means for coding the energy applied ateach end of each section in accordance with traflic condi tions in thetwo sections respectively adjacent thereto, and cab-carried signalcontrolling means governed by the coding of the current energizing eachsection.

THOMAS J. JUDGE.

